What happened
On February 28, 1964, a Bell 47 J2 helicopter, registration HB-XAR, was operating out of the Klosters heliport in Graubünden, Switzerland. The aircraft, operated by Héliswasting AG, was engaged in a local mission to locate a lost model airplane near the trees bordering the landing area.
During the landing phase at approximately 14:05, the pilot attempted to decelerate the aircraft using a flare maneuver. Because the flight had been conducted at a relatively low altitude, the approach angle was shallow. The pilot initiated the pitch-up maneuver too close to the ground, causing the tail of the helicopter to strike the accumulated snow. The impact was severe enough to deform the fuselage and bend the landing skids.
The investigation
The investigation focused on the mechanics of the landing approach and the physical impact of the tail rotor against the terrain. Investigators examined the state of the tail rotor assembly, the drive shaft, and the protective strut. It was noted that the protective rod, intended to prevent rotor-to-ground contact, sank into the wet snow and bent to the right. This allowed the tail rotor to strike the protective skid, which was subsequently severed in three places.
Findings
- The primary cause of the accident was a pilot error in estimating the aircraft's height above the ground during the final braking phase.
- The pilot opted to use a rapid braking method (flaring the aircraft) rather than maintaining a constant approach attitude.
- The maneuver was executed too late in the approach, leading to the tail rotor's contact with the snow-covered surface.
- The impact resulted in significant damage to the tail rotor, the drive shaft, and the fuselage, with repair costs estimated between 17,000 and 25,000 Swiss Francs.